Make explicit conversion to string in JSON parsing

For some reason old code no longer works, but including explicit request for string fixes the problem.

okapi.cpp

@@ -162,7 +162,7 @@ Caches Okapi::get_caches(const std::set<std::string>& codes) const {
 			c.terr = el.value()["terrain"];
 			c.owner = el.value()["owner"]["username"];
 			c.owner_uuid = el.value()["owner"]["uuid"];
-			c.pos = Position(el.value()["location"]);
+			c.pos = Position(el.value()["location"].get<std::string>());
 			c.origin = service;
 			c.fav = el.value()["recommendations"];
 			if (!el.value()["rating"].is_null()) c.rating = el.value()["rating"];